The present disclosure relates to the field of magnetic measurement targets suitable for being positioned inside a vehicle axle.
Several methods have been proposed for use at the moment of landing to determine in reliable manner whether the wheels carried by an undercarriage of an aircraft have or have not touched the ground.
In particular, proposals have been made to measure the pressure of a shock absorber in a leg of the undercarriage, or indeed to measure movement of a sliding rod in the leg of the undercarriage. Nevertheless, the shock absorber of an undercarriage leg presents a movement threshold and a contraction threshold that make those solutions ineffective and inappropriate.
Proposals have also been made to integrate movement sensors inside a wheel-carrying axle of the undercarriage, and in particular magnetic movement sensors of the linear variable differential transformer (LVDT) type. The LVDT sensors are positioned on an inside diameter of the axle.
Nevertheless, the space available inside the axle is very small, so it is appropriate to use LVDT sensors of very small size, which are fragile, not very accurate, and expensive. Furthermore, LVDT sensors are difficult to install and remove, once more because of the small size of the axle. Finally, the little space that is available makes it necessary to place LVDT sensors on a common support. Any one of the LVDT sensors jamming thus leads to losing the information produced by the other LVDT sensors.